High efficiency microstrip patch antenna elements developed in the framework of a green radio technology European Union research project are presented. Wide band aperture-coupled stacked-patch configurations with foam substrates are used. The cheap and low losses low dielectric constant foam substrate used leads to a high efficiency and wide bandwidth printed antenna solution. The good agreement between numerical simulation and experimental input impedance, radiation pattern and efficiency results provides validation of the design and optimization procedure and confirm the proof of concept. A 16% (impedance) bandwidth and 93% radiation efficiency are obtained.